Method for operating a communication system having a plurality of nodes, and a communication system therefor

Abstract

In a method for operating a communication system having a plurality of nodes which have access to a shared channel, a transmission process for transmitting a message via the channel is monitored for bit errors, and when a bit error occurs, a signaling message is transmitted via the channel in order to signal the bit error. In order to allow communications processes between the nodes to be controlled as a function of a bit error rate of the channel, a signaling rate of the signaling messages is measured and a bit error rate of the channel is determined as a function of the signaling rate.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a method for operating a communication system having a plurality of nodes, which have access to a shared channel of the communication system; in the method, a transmission process for transmitting a message via the channel is monitored for bit errors, and if a bit error occurs, a signaling message is transmitted via the channel in order to signal the bit error.[0003]2. Description of Related Art[0004]In the ISO standard 11898-1, “Road Vehicles—Controller Area Network (CAN)—Part 1: Data Link Layer and Physical Signaling”, the data link layer of the controller area network (CAN) as well as the signaling are specified in the physical layer of the CAN. This standard specifies signaling messages, referred to as error frames, for signaling a bit error that has occurred in the course of a data transmission. In addition, it is specified in the standard that nodes detect the individual occurring ...

AI Technical Summary

Benefits of technology

[0007]According to the present invention, it was recognized that an evaluation of the signaling messages provides a simple means for estimating a current bit error rate of the channel, thereby dispensing with the need to expand any protocols of the communication system for such a purpose. The method is therefore easy to realize, and a communication system operated on the basis of the method according to the present invention remains compatible with conventional communication systems. Furthermore, the method does not require any additional messages that must be transmitted via the channel. As a result, the channel is not subjected to further loading when the method is executed. Moreover, this is a digital method for which no estimates of analog variables such as a signal-to-noise ratio are required. The method is particularly suitable for determining the current bit error rate in fast communication systems (e.g., in the telecommunications field). The method is used especially in communication systems in which all communication participants are able to observe responses to bit errors in the bit stream. Statistics are kept about the monitored responses in order to then determine the current bit error rate on this basis. The transmission of the messages via the communication system preferably takes place in data frames. The current bit error rate is able to be determined in one or a plurality of communication participant(s) of the communication system, preferably in all of them.

[0009]An undesired influence of the channel occupancy on a value of the estimated bit error rate may be eliminated in fairly effective manner in that the channel occupancy is determined by measuring a message rate of messages transmitted via the channel, preferably of messages transmitted without errors. In the process, a length of the individual transmitted messages may be recorded in addition, or an average message length or a previously known message length may form the basis for determining the channel occupancy. This makes it possible to determine the value of the bit error rate largely independently of the current channel occupancy; in other words, fluctuations in the channel occupancy falsify the value of the determined bit error rate only negligibly at most. The provided restriction of the measurement of the message rate to messages transmitted without error simplifies the method without any noticeable detrimental effect on the accuracy of this measurement and thus the accuracy of the determined bit error rate.

[0011]According to one preferred specific embodiment of the present invention, an average bit error rate of all transmission processes is determined as bit error rate. This makes it possible to realize the method with little outlay because only one value for the bit error rate must be held in reserve and thus relatively little memory space is required for executing the method.

[0013]It has shown to be advantageous if the bit error rate of the channel is determined for a specific time interval. It is therefore preferred if a time interval is specified for which the bit error rate is determined, preferably via a start command for starting the interval and a stop command for stopping the interval.

[0014]In an especially preferred manner, a communication behavior of at least one node is adapted as a function of the determined bit error rate. In this way it is possible to dynamically adapt the communication system to the temporally varying bit error rate. If the bit error rate is relatively high at a specific point in time, then one or a plurality of node(s) may choose for its transmissions a format of useful data blocks in which a percentage of check bits of the entire useful data block is relatively high, so that a relatively low residual error probability is achieved in the transmission despite the high bit error rate. In general, an instant and the content of an individual transmission are able to be adapted as a function of the determined bit error rate. At a high bit error rate, for example, relatively unimportant and not time-critical transmissions may be postponed, so that overloading of the communication system due to a useful data rate of the channel that is reduced on account of the high bit error rate is avoided. It may also be the case that transmissions that are unable to be adapted to an increased bit error rate, as they occur, for example, in applications having a low error tolerance time, are avoided as long as the bit error rate is relatively high. As a consequence, the communication system need no longer be set up based on an assumed, relatively conservatively estimated bit error rate in terms of statistics, so that the useful data throughput of the communication system is increased because complex safeguarding measures against the bit errors must be used only in cases where the bit error rate is high.

[0019]It may also be the case that the measuring device is implemented as a separate component, preferably in the form of an ASIC. This makes it possible to use conventional components in the communication system according to the present invention, such as conventional communication controllers, for example.

Problems solved by technology

A disadvantage of the known CAN protocols is that their use does not allow a sufficiently precise adaptive communication control as a function of a current bit error rate of the channel.

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